1. Field of the Invention
The present invention relates to test equipment for a semiconductor device; and more particularly, to a probe tip sanding control method and apparatus.
2. Description of the Related Art
An electrical die sorting (EDS) test for the testing of semiconductor devices is well-known in the art, and is performed at the wafer level, as opposed to the package level. At the wafer level, the semiconductor device has not yet been placed in a package, and therefore does not include leads. Thus, the EDS test employs a probe card having probe tips that access device circuitry. When a probe card tip is in contact with a pad of the semiconductor device, alumina oxide Al2O3, a primary component of the pad, becomes attached to the tip, and therefore contact resistance is increased. This augmented contact resistance disturbs normal contact in an open/short(O/S) test as one of basic DC measurements, affects the linearity of an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC) utilized in an analog block test, and affects certain measuring procedures, such as a gain error etc. This, in turn, can lead to erroneous readings as to whether a device under test meets the criteria for proper operation. Therefore, a normal semiconductor device can be dismissed as a bad part as a result of the test procedure, which, in turn, can have an adverse effect on yield, and therefore leads to a rise in manufacturing costs.
If the yield is reduced below a minimum threshold yield set as an initial parameter of the test, the test equipment automatically stops the testing operation. Such a yield reduction caused by an augment of the tip contact resistance drops can therefore affect even the operating rate of the equipment.
To solve such yield reduction and operating rate decrease, conventionally, probe tip sanding is uniformly executed, for example periodically, or following a test, through a sanding command issued by a operator. Since the pad material can be different from one pad to the next as a result of fabrication processes, the resulting yield is therefore subject to the discretion of the test operator.
In the meantime, frequent sanding of the probe tip slows down the test procedure, owing to increased time required for tip sanding, and, in addition, the useful life span of the probe tip is shortened.